1. Field of the Invention
The invention relates to a method of fabricating an organic silicon film, a semiconductor device including the organic silicon film, and a method of fabricating the semiconductor device.
2. Description of the Related Art
A large-scale integrated circuit (LSI) including a silicon substrate or a silicon layer on which a plurality of circuit elements are integrated has frequently included wires composed of aluminum (Al) or Al alloy.
Recently, a wire dimension becomes smaller as integration of circuit elements in an integrated circuit becomes higher. Hence, reduction in wire resistance and high reliability to wires are presently required, and thus, copper (Cu) is selected in place of aluminum as a material of which a wire is composed.
However, copper readily scatters into a silicon oxide film frequently used as an element-separation film or an interlayer insulating film in a silicon semiconductor integrated circuit, and caused current leakage. Thus, a copper wire is covered at a sidewall and a bottom thereof with an electrically conductive barrier metal film for preventing copper from being oxidized and further from scattering, and at an upper surface with an electrically insulating barrier film.
There is recently caused a problem of an increase in a capacity between wires as a wire dimension becomes small. In order to reduce such a capacity, an interlayer insulating film is often comprised of a film having a low dielectric constant, such as a HSQ (Hydrogen Silsesquioxane) film, a CDO (Carbon-Doped Oxide) film, or an organic film.
Such a film having a low dielectric constant is formed by spin-coating or vapor deposition, for instance. If the above-mentioned electrically insulating barrier film formed when a copper wire is used had a high dielectric constant, the electrically insulating barrier film would increase a capacity between wires. Accordingly, it is necessary for the electrically insulating barrier film to have a low dielectric constant.
An electrically insulating barrier film is required to have characteristics such as (i) having sufficient barrier performance for preventing copper from scattering, (ii) low current leakage, (iii) being able to be formed without oxidizing copper at a surface or degrading copper, (iv) being able to act as an etching-stopper film (that is, having etching-controllability), and (v) a low dielectric constant of a material of which the electrically insulating barrier film is composed.
A silicon carbide-nitride (SiCN) film having a dielectric constant (k) of about 5.0, and a silicon carbide (SiC) film having a dielectric constant of about 4.5 are known as an electrically insulating barrier film satisfying the above-mentioned requirement. These SiCN and SiC films are formed by spin-coating or chemical vapor deposition (CVD) such as plasma-enhanced chemical vapor deposition.
A SiC film formed by spin-coating or chemical vapor deposition is referred to as “an organic SiC film”.
For instance, Japanese Patent Application Publication No. 2000-3118 suggests a method of forming an organic SiC film (organic silicon carbide film) composed of polysilane, by spin-coating.
Japanese Patent Application Publication No. 2002-526916 suggests a method of forming an organic SiC film (organic silicon carbide film) by chemical vapor deposition through the use of silane compound as a raw material gas.
Japanese Patent Application Publication No. 2004-221275 suggests a method of forming an organic SiC film by chemical vapor deposition through the use of organic silane (including organic silane having a vinyl group) as a raw material gas.
The formation of an organic SiC film by spin-coating provides an advantage that a raw material can be selected among broad range of materials relative to the formation of an organic SiC film by chemical vapor deposition. However, the formation of an organic SiC film by spin-coating is accompanied with problems that it is difficult to control a film thickness in a nanometer order, and it is also difficult for the film to have a sufficient strength and high adhesion with an underlying film.
In contrast, if an organic SiC film is formed by chemical vapor deposition through the use of silane compound having no vinyl groups, such as trimethyl silane or tetramethyl silane, as a raw material gas, a lot of non-bonding hands would exist in the film, since the deposition of the film progresses as breakage and re-bonding of a raw material are repeated. Non-bonding hands existing in an organic SiC film is a bar to obtain an organic SiC film reducing current leakage.
It is possible to obtain an organic SiC film including a small number of non-bonding hands therein by forming the organic SiC film by chemical vapor deposition through the use of silane compound having a vinyl group, as a raw material gas. However, if an organic SiC film is to be formed at a practical film-formation speed through the use of silane compound having one vinyl group per a molecule, as a raw material gas, dimer is likely to be generated in the resultant organic SiC film. Such dimer is a bar to enhance a strength and a resistance to heat of the resultant organic SiC film.
For instance, if an organic SiC film is formed at a practical film-formation speed by plasma-enhanced chemical vapor deposition through the use of trimethylvinyl silane as a raw material gas, unsaturated bond (double bonds of carbon atoms) existing in a vinyl group is excited by plasma, and receives thermal energy, resulting in that the reaction expressed with the formula (CR5) occurs.

Actually, ring-opening reaction such as expressed with the formula (CR5) successively occurs in plasma or at a surface of a substrate (a surface of an object on which an organic SiC film is to be formed), and accordingly, reactive groups cause polymerization reaction. During such polymerization reaction, dimer expressed with the formula (Xa) is likely to be generated, and thus, a cross-linking structure is likely to be generated.

Thus, as mentioned above, dimer is a bar to enhance a strength and a resistance to heat of an organic SiC film.
It would be possible to form an organic SiC film having a three-dimensional network structure, expressed with the formula (Xb), by applying energy to a film such that a methyl group existing in trimethylvinyl silane molecule is broken, to thereby generate a lot of non-bonding hands in trimethylvinyl silane molecule.

However, if energy which can break a methyl group is applied to a film during the formation of the film, a film-formation speed would be reduced to a non-practical level.
Furthermore, an atom number ratio of carbon atoms of a resultant organic SiC film becomes small, resulting in that it would be difficult to obtain an organic SiC film having desired characteristics such as a dielectric constant, a strength, and a resistance to heat.
The symbol “*” in the formulas (CR5) and (Xb) indicates a non-bonding hand.
If silane compound having two or more vinyl groups per a molecule is used as a raw material gas, since a three-dimensional network structure is formed by addition polymerization among molecules, a resultant organic SiC film would have a high strength and a high resistance to heat. However, it is difficult to sufficiently react vinyl bonds by a conventional process, and hence, vinyl bonds are likely to remain non-reacted in a resultant organic SiC film. Such vinyl bonds remaining in a resultant organic SiC film are bar to obtain an organic SiC film reducing current leakage.